Producing solvents from refined pitch



July 28, 1942 J. E. HARVEY, .JR A 2,291,318

`PRODUCING SOLVENTS FROM REFINED PITCH Filed March 14, 1941 wie@ W162C/f www5/mno (WM/af @Af/MYV] gmc/whom @www Patented July 28, 1942 PRODUCING SOLVEN PIT TS FROM REFINED CH Jacquelin E. Harvey, Jr., Atlanta, Ga., assignor of one-half to Southern Wood Preserving Company, East Point, Ga., a corporation of Georgia Application March 14, 1941, Serial No. 383,468 6 Claims. (Cl. 196-53) This invention relates to the production oi useful liquids from tars and fractions thereof. It relates more specically to the catalytic production of solvents from tars and fractions thereof.

This application is a continuation in part of my application Serial No. 345,439, led July 13, 1940, for Catalytic synthesis of Valuable liquids and products thereof, copending herewith, as to all matter common to the two applications.

An object of the present invention is the production of solvents of aromatic nature.

A further object of the present invention is the catalytic production of solvents of increased solvency from tars or fractions thereof, characterized by provision of maintaining said catalysis at optimum conditions, while reducing coke residue.

Other objects of the present invention will be apparent from the following disclosures.

Broadly viewed, the present process provides a method for converting tars, or fractions thereof substantially in entirety, if desired, into solvents of controllable boiling range, the conversion characterized by subjecting said tar, or fraction thereof, to the action of hydrogen while contacting a sulfide catalyst, with catalysis being maintained at optimum conditions by provision.

The conversion of the starting tars of the present process to said solvents by the action of hydrogen is further characterized by step-wise conversion.

Tars, or fractions thereof, of aromatic content provide suitable starting materials; such tars being obtained from wood, coal and petroleum. As far as being commercially available, coal tar is one of the most attractive starting materalsbecause of its low cost. In the following examples coal tar, or fractions thereof, will be shown as the starting material, but such a selection is for purposes of illustration only and is not restrictive in any sense inasmuch as any tar, or fraction thereof, of aromatic content serves as suitable starting material.

Coal tar as a starting material contains such a high percentage of carbon that the solvents of the present invention, that is to say, solvents of increased solvency flowing from, among other things, increased boiling range of an intermediate parent material, are not produced in one step or cycle, but the coal tar is first depolymerized by the action of hydrogen, to the end that when a deep cut, as hereinafter explained, is taken on the depolymerized tar, or fraction thereof, that subsequently subjecting said deep cut to the action specific of a flow of hydrogen sufficient tol increase boiling range thereby increasing solvency, does not induce substantial carbonaceous increment.

The present invention provides for a method of producing said solvents of increased solvency in a catalytic manner, said catalysis being maintained at substantially optimum conditions by specic provision.

The following examples will serve to illustrate the general principles upon which the practice of the present invention is based, as well as the process of the present invention.

The invention Will be understood from the following description of illustrative steps comprising various methods of securing `the objects of the invention, when read in connection with the accompanying drawing wherein the figure is a diagrammatic sketch of an apparatus for carrying out a form of the process of the invention and wherein the nature of the step carried out in each chamber and the contents thereof are indicated by legend.

Example I.-A coal tar fraction boiling substantially 3% at 380 C. was passed through a high presure reaction chamber in the presence of a molybdenum sulfide catalyst, While flowing in 18,000 cubic feet of hydrogen per barrel feed therewith. Temperatures 400 C., pressure 300 atmospheres. Contact time is 1 hour. A test of the material under treatment after 8 hours showed 43% distilling at 380 C. After 32 hours the material distilled but 22% at the same temperature. Research disclosed that duringA the operation the sulfide catalyst, or at least a portion thereof, had changed to form other than sulfide. Research further disclosed that maintaining a hydrogen sulfide partial pressure of at least a fractional atmosphere, aided in maintaining the catalyst in sulfide form, thus assisting in the depolymerizing step which forms an important part of the present invention. One-half of l per cent sulphur was added to the feed stock and operation repeated. Other than normal aging of the catalyst, the depolymerizing proceeded without substantial reduction to the end that in the order of 43% was continuously recoverable at 380 C., the hydrogenated mass being characterized by lowered specific gravity, coke residue, viscosity and solvency.

A fraction recovered to 380 C. was then subjected to the action of a fiow of hydrogen of less than 10,000 cubic feet per b-arrel feed stock, while contacting a catalyst, at a temperature in excess of 400 C. and superatmospheric pressure and continued for such a length of time as to induce increased boiling points and solvency. The

tional atmosphere. hydrogen sulfide atmosphere, at times, 1% sul- -that is to say,

range.

C. Benzol 78-120 Toluol 100-'150 I-Ii-fiash naphtha 150-200 Heavy naphtha 150-29'0 Plasticizers 160-360 or others.

Some of the selected startingmaterialsinay contain sufficient initial sulphur to main optimum catalyst activity. At times, recycle feeds need more sulphur addition tothe end that the necessary hydrogen sulfide atmosphere be provided. The necessary `hydrogen-'sulfide atmosphere is that atmosphererequired to Amaintain -at least a portion of the sulfide catalyst in substantial sulde form and may be describedas representing a partial pressure of at' least a frac- For the maintenance of said phur, or more, may be added.

Regarding the removal of the lower boiling fractions from the depolymerized starting material for subsequent increase in boiling ranges by the action of hydrogen, as heretofore described, said-fractional removalmay be made at any point whereby to provide, after further treatment, substitutes for any` or all ofthe noted solvents and plasticizers.

`Entctmple II.-A tar fraction boilingpredomiby presence of high molecular complexes, was passed through a high pressure reactionvessel, in the4 presence of a tin'sulole catalyst, while owing 15,000 cubic feet of hydrogen per barrel feed;

`Was so controlled as to provide said solvency increment.

Escample IV.-It has been discovered that when subjecting certain mixtures of refined coal tar fractions to the action of hydrogen in accord- Vance with the present process for the production Ynantly in excess of 220 C., and-characterized temperature 375 C. Pressure was 300 :atmospheres and hydrogen'sulde-partial pressure 11/2 atmospheres. Period of treatment'was 11/2 hours, whereby to provide lovveredspeciflc gravity, viscosity, coke residue Yand solvency.

The thus beneficiated material was stripped of -its low ends to 200 C. Said low en'dsWere then subjected tothe action of lessthan 8g000cubic feet hydrogen per barrel feed at'a temperature of 450 C. and a pressure in excess of 100 atmospheres. Catalyst was cobalt. Treatment continued for such alength of time asto increase boiling range and solvency.

ForV the hydrogen treating period characterized by'solvency increase, the period may be very short, as for instance one minute; or more or less,

or several minutes, if desired; however, said period is selected to meet processrequirernents, increasein solvency vand boiling Vfide catalyst, while'owing 20,000 cubic feet of hydrogen `per barrel feed. Temperature was 410 C. and pressure 350 atmospheres; hydrogen sulfide partial pressure, 3A; atmosphere. Time of Ytreatment-was minutes, whereby to producea depclymerized, or partially depolymerized prodsolvency; resultant Conradson carbon, 10.3, spe- -uct having lowered viscosity,specic"gravity'an'd ent process.

` rial under treatment. y The critical time `elementbeca/use 'ofithe obof solvents and/orV plasticizers that the formerly accepted teaching that product increment, depolymerization'and/or hydrogen absorption are linear functions of the time, is not followed.

When subjecting a mixture of crude coal tar fractions Aboilingpredominantly above 250C. or 275 Cxto theaction of hydrogen,research has disclosed that the newly inducedproduc'tsdepolymerization Vand/or hydrogen 'absorption are linear functions of ltl'1'e"time. As an example, When the jabove mixture of crude rtar fractions issubjected tothe 'actionof hydrogen lfor 2-, 5-,and`8-hour periods, the newly inducedlproducts, depolymerization "and/ or hydrogen absorption were linear functions of the time element.

One of the preferredstarting` materials ofthe present processis amixture of refined coaltar fractions boiling predominantly Vabove A355 Vor V380 C. 'Such a'starting'rnaterial is conveniently -the nal residueA resulting from evaporating'coal `tar 'to' dryness or substantial dryness ian'dithen stripping"woodtpreservative from the distillate. This finaljresidue mass ofr'ened coal tar" fractionsis an especially suitable refined coal tar pitch to beA used asv starting lmaterial of` the pres- I-Iowever, in Vcontradistinction to themixture of crudeA coal vtar fractions `boiling `predominantly above 250 or'i300-C., when the "aforenam'ed Lpreferred `starting, material is vsubjected' to the-'action of"hydrogenffor production of solvents and/or plasticizers, the newly induced fractions, depolymerization and/or hydrogenabsorption are not, as describedfor'the 'othermix- Y 'tureI of crudecoal tar fractionsflinearfunctions ofthe time.

"A critical period of treatment' by or with hydrogen exists, and which if exceeded causes loss of*r newly induced'fractions, polymerizationan'd/or lessened hydrogen absorption on certain*- fractions ofthe preferred startingmateviouspossible variations in the characteristics of the aforerrairled refinedY coal tar pitch` cannot Vbe spoken `ofas Aan `arbitrary' figure'. 'It'can be stated, however, that if vthe ,'rened pitch were to besubjectedito the actionof'hy- `drogen for `such a length of time,

-which for other crude coal tar fractions would' illustrate that Ythev newly induced fraction; dpolymerization and/orl-'hydrogen vabsorption were linear vfunctions of "the timeelernent'loss' ofinduced products, n polymerization "an'd/ or Vl'essening of jhydrogenjabsorption would occur. vWhen treating thereiined coaltar` pitch by or with 'hydrogen; theL critical time element is in the order of t aboutthree hours.

Refined `coal tar pitch chosen' from the group boiling predominantly `abovefand "above, 355' C. 4was lpassed through" a high'pressure reaction chamber inthe presence of -'a 'molyb'denum'isuifide catalyst while flowing in 16,000 cubic feet of hydrogen per barrel feed therewith. Temperature was 410 C. and pressure 300 atmospheres. Effective contact time was two hours. A test of the material under treatment after flowing material for eight hours showed 43% distilling at 380 C. After thirty-two hours flow the material distilled but 22% at the same temperature. Research disclosed that during the operation the sulfide catalyst, or at least a portion thereof, had changed to form other than sulfide. Reaction further disclosed that maintaining a hydrogen sulfide partial pressure of at least a fractional atmosphere aided in maintaining the catalyst in sulfide form, thus assisting in the depolymerizing step which forms an important part of the present invention. Onehalf of one per cent sulfur was added to the feed stock and the operation repeated. Other than the normal aging of the catalyst, the depolymerizing proceeded without substantial reduction to the end that in the order of 43% was recoverable at 380 C., the treated refined pitch being characterized by lowered specific gravity, coke residue, viscosity and solvency. By the employment of a time period of less than three hours, polymerization and loss of newly induced fractions were precluded. When treating the refined coal tar pitch in the manner described, it was determined that the newly induced fractions, polymerization and/ or hydrogen absorption were linear functions of the time element.

The treated refined coal tar pitch is stripped at 380 C. and the stripped low boiling fractions subjected to a liow of hydrogen of less than 8,000 cubic feet per barrel feed stock at a temperature in excess of 400 C. and super-atmospheric pressure and continued for such a length of time as to induce increased boiling points and solvency. The thus beneiiciated material is then fractionally distilled to recover solvents of various boiling ranges with the fraction boiling 300 to 360 C. serving as a substitute for certain plasticizing oils.

When the term increased solvency is used herein, or in the appended claims, is meant that Y the solvency when measured by usual standards,

as for instance aniline point or kauri-butanol number, shows an improvement. The term reduced or lowered solvency means the opposite of increased or enhanced solvency.

The hydrogen action of the present invention is so controlled, that the coordinated pressure and temperature selected produces no substantial carbonaceous deposition; other than such deposition as is inherent to the process and which usually results in plant shut down every 3 to 6 months or longer. Otherwise, the induced solvency of the present invention is not feasible of practice.

The action of hydrogen in the present invention may, therefore, be viewed as the controlled action of hydrogen that induces no substantial percentage of fractions not responsive to further hydrogenations, as for instance, coke. Thus controls are exerted to the end that, if desired, in the order of upward of 80% or more are converted into the solvents of the present invention.

By the terms high molecular complexes, multiplicity of rings and ring multiples as used herein, and in the appended claims, is meant those high boiling fractions especially susceptible to thermal degradation.

By the term beneliciated as used is meant the starting material at least once subjected to the controlled action of hydrogen in accordance with the present process.

When the depolymerized starting material is stripped of its lower ends for further treatment by hydrogen, any selected portion of said stripped lower ends may comprise the starting material of the cycle characterized by increase in boiling points and solvency.

Instead of recovering the low boiling ends from the depolymerized starting material by distillation, said recovery may, if desired, be effected by gas action.

By the term deep cut is meant that the cut so taken represents a predominant portion of the material cut.

Hydrogen flows are usually in excess of 3,000 cubic feet per barrel of feed stock. In the two hydrogen cycles aforenamed, the hydrogen flow is coordinated with pressure and temperature to give, in the cycle characterized by depolymerization, a lowered solvency, whereas the second cycle is characterized by increased solvency, and increased boiling points.

In the first hydrogen action, gas flows of l5,000-l8,000 cubic feet per barrel feed stock have proven satisfactory; however under certain conditions higher or lower gas iows may be employed. In the second hydrogen action, gas iiows of 350D-6000 cubic feet per barrel feed stock have proven satisfactory; however, higher or lower flows may be employed under certain conditions.

The catalyst of the present invention may originally be oxides which are converted, at least to a degree, to suliides in the presence of aforenamed hydrogen suliide.

Hydrogen may be supplied as such, or gases capable of yielding hydrogen may be used, Diluting gas or gases may -be used to control conversion, and for other purposes.

By the term depolymerize as used herein and in the appended claims, is meant, among other things, the reduction, including in size, of aforesaid molecular complexes to the end that they are not so susceptible to thermal degradation.

Residue resulting from distillation in the process may be used as an article of commerce, or recycled for further processing whereby to provide, if desired, additional solvent production.

The solvents of the present invention may be reiined by alkalis, acids, solvents or further action of hydrogen.

All catalysts eiiective in the presence of hydro gen for aforementioned purposes are usable in conjunction with sulphide catalysts, as for instance, chromium, molybdenum, vanadium, uranium, cobalt, copper and their compounds, foi` example suldes or oxides. Catalysts may be promoted or not; with or without small amounts of alkali, acid or halid, or derivatives thereof. Small amounts of halogen or halogens, as such, or incorporated with other substances as derivatives; effective catalyst deposited on carriers, as for instance gels, earths, carbon, or the like; in various shapes, as for instance extruded shapes or lengths, pellets, comminuted; mixed with other material possessing desired action or not; with or without other material effecting splitting or not; catalysts with added halogen derivatives.

If desired, any of the starting feeds prior to their being subjected to the first hydrogen action, may be depolymerized or partially depolymerized by use of a solvent. When employing said solvent, it may be advantageous to select one of refractory nature, and up to volume for volume, or more, may be employed. Such employment of solvent may be read into any of the preceding examples. Y

In the conversion of the starting material, partially or approaching unit, into the solvents of the present process, temperatures of as low as 300 C. are usable; pressures of as low as 50 atmospheres or lower may be used. However, temperatures and pressures of an increased range pro-vide better commercial practice of the present invention. The time element is desirably that period that affords commercial recoveries of the products of, and incidental to, the present invention.

The evaluation of solvent power is` conveniently accomplished by finding the well-known aniline point or kauri-butanol number. The evaluation of plasticizing properties is conveniently accomplished by recourse to methods suggested in chapter VI, The Technology of Solvents by Dr. Otto Jordon, Mannheim, Germany, translated by Alen D. Whitehead, Chemical Publishing Company of New York, Incorporated, New York, New York.

Minor changes may be made in the steps of the process without departing from the spirit of the invention. In the claims amxed to this specication no selection of any particular modicaticn of the invention is intended to the exclusion of other modifications thereof.

I claim:

1. In the production of a solvent from Ythe refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fraction to the action of a relatively high flow of hydrogen at a temperature and pressure in excess of about 400 C. and 50 atmospheres, respectively, in the presence of hydrogen sulfide while contacting a sulfide catalyst for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions; stripping newly induced fractions from the beneciated material; and increasing the boiling points of at least a chosen portion of said stripped fractions by subjecting same to the action of a relatively low now of hydrogen within the limits of about 3000- 6000 cubic feet per barrel material treated at a pressure and temperature of at least about 50 atmospheres and 450 C., respectively, to produce a solvent.

2. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar'to atleast about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher .boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fraction to the action of :a relatively high ilow of yhydrogen in the presence of hydrogen sulfide while contacting a sulfide catalyst fora period not in excess of about three hours, whereby to avoid loss of newly induced fractions; stripping newly induced fractions from the beneciated material; increasing the boiling points of at vleast a chosen portion of said strippedA fractions by subjecting same to the action of a relatively low flow of hydrogen within the limits of about 3000-6000 cubic feet per barrel materialtreated; andfractionatingl the last Vnamed beneciated material to segregate a solvent.

3. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to iat least about substantial dryness, andv fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355Q C., the process which comprises: subjecting said higher boiling fraction to the action of a relatively high flow of hydrogen in the presence of hydrogen sulfide while contacting a sulfide-catalyst for a period not in eX- cess of about three hours, whereby to avoid loss of newly induced fractions; stripping newly induced fractions from the beneciated material; increasing the boiling points of at least a chosen portion cf said stripped fractions by subjecting same to the action of la relatively low flow of hydrogen within the limits of about 3000- 6000 cubic feet per barrel material treated; and fractionating the last named beneciated material to provide a solvent boiling preponderantly between and 150 C. Y

4. In the production of a solvent from the rened pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood ypreservative, and a higher boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fraction to the action of a relatively high flow of hydrogen in the presence of hydrogen sulfide while contacting a sulde catalyst for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions; stripping newly induced fractions from the beneficiated material; and increasing the yboiling points of at least a chosen portion of said stripped fractions by subjecting same to the action of la relatively low ow of hydrogen not in excess of about 6000 cubic feet per barrel feed stock, to produce a solvent.

5. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C., the process which comprises: subjecting said higher boiling fraction to the action of a relatively high flow of hydrogen in the presence of hydrogen sulfide while contacting la sulfide catalyst at a pressure in excess of about 50 atmospheres and a temperature of at least about 400 C. for a period not in excess of about three hours, whereby to avoid polymerization; stripping newly induced fractions from the beneficiated material; and increasing the boiling points of at least a chosen portion of said stripped fractions by subjecting same to the action of a relatively low flow of hydrogen within the limits of 300D-6000 cubic feet per barrel material treated at a pressure and temperature of at least about 50 atmospheres and 450 C., respectively to produce a solvent.

6. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly `above 355 C., lthe process which comprises: subjecting said higher boiling fraction to the action of a relatively high flow of hydrogen in the presence of hydrogen sulfide while contacting a sulfide catalyst at a temperature and pressure in excess of about 400 C. and 5 about 50 atmospheres, respectively, for @a period not in excess of about three hours, whereby to avoid lowered hydrogen absorption; stripping newly induced fractions from the beneciated material; and increasing the boiling points of at least a chosen portion of said stripped fractions by subjecting same to the action of a relatively low flow of hydrogen Within the limits of :about 23000-6000 cubic feet per barrel material treated at a. pressure and temperature of at least about 50 atmospheres and 450 C., respectively, to produce a solvent.

J. E. HARVEY, JR., 

